Abstract

In the last few years the cultivation of seaweed around the world has increased; mainly the macroalgae, that are used for human food. The main reason is the high nutritional value of seaweed (proteins, fiber, vitamins and minerals). In ESAB-UPC have an installation of the Integrated Multitrophic Aquaculture (IMTA) techniques use Ulva sp. as biofilter for recirculation water of fish farm. These techniques allow to reduce dissolved nutrients and the energetic cost installation and, at the same time, the viability of the algae produced for human food is also studied. The objectives of the work are: i) to determine the microbiological status of the Ulva ohnoi for human consumption, complying with current food regulations, ii) isolating the main epiphyte cyanobacteria, iii) try different culture media to determinate the most efficient growth of main epiphyte cyanobacteria iv) extracting the DNA from the main cyanobacteria epiphyte. The food safety biomarkers studied were: total and fecal coliforms, total mesophilic aerobes, halophiles and Staphylococcus sp., Clostridium sulfite reducers, Clostridium perfringens and Vibrio cholerae. In order to isolate the main epiphytic cyanobacteria of the Ulva ohnoi macroalgae, plantings have been carried out in 10 culture media that are basically differentiated by the richness of mineral salts, vitamins and also whether they contain agar or not. Growth has been assessed visually qualitatively and also by making microscopic preparations. Finally, once the main epiphytic cyanobacteria has been isolated, it has been grown to obtain sufficient biomass, and to extract the DNA by the phenol-chloroform method. The results obtained allow us to affirm that the seaweed is safe for human consumption, because it complies with the French regulations (CEVA, 2014) and the EU regulation nº 258/97. Not detected fecal contamination, and neither the pathogen Vibrio cholerae. The total mesophilic aerobic count is below the recommended limit (<105 CFU / g or mL). Of the evaluated media, the L1 (Guillard and Hargraves, 1993) with actidione is the one with the best growth, because it is a medium rich in growth factors (thiamine, biotin and B12). Also the presence of the antibiotic has allowed to purify the bacterial suspension. It has also been possible to multiply the main cyanobacteria in 100 mL volumes, obtaining enough biomass for extracting the DNA with a good quality and is ready to perform a PCR for identification.